1. Field of the Invention
The present invention relates to a technique of recording information onto an optical disc by using laser beams, for example.
2. Description of the Related Art
Optical-disc rotation control schemes generally used include two types, namely, a CLV (constant linearly velocity) control scheme, which is executed in a constant linear velocity mode, and a CAV (constant angular velocity) control scheme, which is executed in a constant angular velocity mode.
In the CLV control, the optical-disc rotational velocity increases toward the inner periphery, such that it is difficult to enhance the recording/reproducing speeds by using the CLV scheme. As such, with increased recording/reproducing speeds, there is employed the CAV control scheme that enables enhancement in the linear velocity in the outer periphery portion.
In addition, generally, in the case that information is recorded by using marks and spaces, the emission power and emission time of laser light are finely controlled to enhance mark-forming accuracy. Such a control scheme is called a “write strategy.”
The write strategy is variable depending on the linear velocity in the event of recording onto the optical disc through the CAV control, so that the linear velocity of the optical disc is different depending on the radial position of the optical disc. For this reason, record parameters of the write strategy, such as the amounts of control of emission power and emission time of the pulse, have to be specified corresponding to the respective radial position.
Further, characteristics such as those in rising and falling of recording laser light irradiated from lasers are slightly different depending on the respective laser, so that the write strategy has to be adjusted corresponds to each optical disc recording apparatus. As shown and described in Japanese Unexamined Patent Application Publication No. 2003-85753, in a CAV recording apparatus, record parameter learning is carried out on the innermost periphery and the outermost periphery, and record parameters in an inbetween radial position are obtained by interpolating, such as linear interpolation, from both learning results.
Generally, however, during the manufacturing process, there occur many cases in which nonuniformity of a recording layer, distortion of optical disc recording grooves, and the like occur in outer periphery portions of the optical disc. As such, when high speed recording is carried out through the CAV scheme, there occurs a noise higher than a servo band in the outer periphery portion. Any one of the aforementioned the recording layer thickness nonuniformity and the recording groove distortion, herebelow, will be referred to as deviation. The deviation causes recording failure and reproducing failure because of servo swings in the outer periphery portion.
For this reason, in the high speed CAV recording, when record parameter learning is carried out on the outer periphery portion with deviation, an inappropriate record parameter is likely to be learned to be an optimal record parameter. Especially, according to DVD-RAM standards, it is recommended that jitter corresponding to fluctuation of an edge component of a recording mark or space is set as an index in a record parameter learning scheme. As such, in the event that the S/N ratio is deteriorated due to recording failure as a result of the deviation, acquirement of the record parameters is significantly influenced, increasing the probability that an inappropriate record parameter is learned to be optimal.
As a method of preventing such the problem, a method is known that calculates a record parameter being employed in the event of recording at high linear velocity on an outer periphery zone by carrying out a predetermined calculation on a record parameter obtained from the result of a trial write of an inner periphery zone (see Japanese Unexamined Patent Application Publication No. 2003-123255).